In one of the newest applications of cochlear implants, individuals with bilateral low-frequency hearing receive a short electrode array in one cochlea with the aim of preserving hearing in that ear. A successful surgical outcome allows patients to combine electrical (E) stimulation from the implanted ear and acoustic stimulation (S) from both ears or EAS. The long-term goal of this research is to quantify the benefit of acoustic hearing from two partially hearing ears vs. one partially hearing ear - as in the case of bimodal hearing. Previous research has failed to demonstrate significant benefit to speech perception for EAS with two partially hearing ears vs. one partially hearing ear. The standard clinical measures that have been used to assess benefit, however, have not been designed to assess binaural listening. Thus the proposed research will test two groups of patients including (1) EAS recipients, and (2) patients with a conventional electrode array in one ear and low-frequency hearing in the other ear (i.e., bimodal). Experimentation will include complex listening environments which are thought to be sensitive to the use of binaural cues including the spatial separation of speech and noise, reverberation, and localization. The clinical application of this proposal is substantial. Neither audiologists nor otologists are certain how to counsel EAS-qualifying patients about treatment options. This project will provide the necessary information to allow for data-driven counseling.